Frequency meter



1956 w. JUDA ETAL 2,770,776

FREQUENCY METER Original Filed July 9, 1949 RESISTANCE OFPHENOL-SULFONIC ACID-FORMALDEHYDE POLYMER R -||.5 Lon I.cm.Di0. 4O

, OHMS 1 (X10) O 2 4 6 8 IO I2 l4 16 I8 20 CYCLES PER SECOND INVENTORSWALTER JUDA WAYNE .A. McRAE ATTORNEYS United States Patent FREQUENCYMETER Walter Juda, Lexington, and Wayne A. McRae, Arlington, Mass.,assignors to Ionics, Incorporated, Cambridge, Mass., a corporation ofMassachusetts Original application July 9, 1949, Serial No. 103,784,

now Patent No. 2,636,851, dated April 28, 1953. Divided and thisapplication April 14, 1953, Serial No. 348,722

1 Claim. (Cl. 324-78) This application is a division of our copendingapplication Serial No. 103,784, filed July 9, 1949, now Patent No.2,636,851, issued April 28, 1953, in which are disclosed what may becharacterized as solid unfractured structures having at least twodimensions each in excess of 0.25 inch, and comprising as an essentialpart extending substantially throughout, a predominant amount of an ionexchange resin which comprises: an insoluble infusible synthetic organicpolymeric matrix, dissociable ionic groups chemically bonded to saidmatrix and water in gel relationship with said matrix. The ionic groupshave a dissociation constant (K) of at least 10* and are present in anamount of at least 3.0 milliequivalents per gram of dry resin when K isbetween and 10 and in an amount of at least 0.3 milliequivalent per gramof dry resin when K is 10* or greater. The water is present in an amountof at least of the weight of dry resin.

A preferred manner of forming such structures consists in forming anaqueous dispersion of material polymerizable into an ion exchange resin,containing at least 15% water on the weight of dry resin, and effectingpolymerization of the material under conditions preventive of the escapeof water from the dispersion. There is thereby formed a structure inwhich the ion exchange resin presents a homogeneous continuous phasethroughout the structure.

The present invention provides novel electrolysis equipment useful fornumerous electrical measurements such as the measurement of frequency,or the number of coulombs passed by an electrical circuit.

According to the invention the structure comprising an ion exchangeresin (as defined above) is placed in direct contact with a pair ofspaced metallic conductors, whereby an alternating current may be passedthrough the structure. It has been found that the resistance orimpedance of the structure varies substantially linearly with thefrequency of the current, whereby a measurement of the resistance may betranslated (on the basis of a previous calibration) into a correspondingfrequency value.

Inasmuch as the present invention is directed to such novel electrolysiseffects which may be realized in such structures, rather than to thestructures or their formation, per se a further description of thestructures and their formation is unnecessary for an understanding ofthis invention, reference being made to our above-identified copendingapplication for a detailed description of such structures.

Our invention will be better appreciated and understood from thefollowing detailed description of preferred embodiments thereof, andfrom the drawings in which:

Fig. l is an elevational diagrammatic view of an assembly of a rod ofthe structure of ion exchange resin between two columns of mercury forthe passage of an electric current therethrough, and,

Fig. 2 is a graph representing the variation in resistance or impedanceof a structure of ion exchange resin with ice assembly of the frequencymeter of the present invention wherein an alternating current is passedthrough said meter and which includes an impedance meter, like numeralsfor like parts being indicated as in Figure l.

I 7 EXAMPLE 1 Electrolysis in the ion-exchange mediurn The phenol wasmelted and heated to C., the sulfuric acid added and the mixture heatedat 140 C. for two hours and then cooled to 15 C. The phenolsulfuric acidmixture was added to the formaldehyde which had been cooled to 0 C.,additional cooling being provided to keep the temperature below 20 C.The resulting mixture may be stored for weeks at 5 C.

The unpolymerized liquid was poured into a cylindrical glass mold andpolymerized at 60 C. until dark in color. The rod was conditioned bysoaking in distilled water until substantially all water-solublereagents were removed. The resulting cation exchange rod 1 (Fig. l), 5.2cm. long and 1.2 cm. in diameter, was mounted between the rods of glasstubes 2, 3, in a rubber tubing 4 as shown. The glass tubes 2, 3, werefilled with mercury at 5 and 6 into which were dipped platinumelectrodes 7 and 8. A direct current (Fig. 1.) of 4 milliamperesdeveloped when a potential of 6 volts was imposed on the system, thecurrent being carried ionically in the east rod, for a constant D. C.potential varying slightly with time, giving rise to an evolution ofhydrogen gas at the mercury-exchanger interface adjacent to the positiveterminal. Much of the oxygen combined with the mercury at the interfaceto give oxides of mercury. If the rod is kept wet with water, theelectrolysis may be continued. Measuring the volume of evolved hydrogenat constant pressure gives a measure of the number of coulombs passed bythe electrical circuit. The system may be used as a convenientcoulombmeter.

Upon closing the circuit an instantaneous very high current of 0.04ampere was observed which dropped to the steady value given above. Thisunusual behavior illustrates the novel nature of this type ofelectrolysis.

EXAMPLE 2 The novel electrical properties of cast ion-exchange materialsfor the measurement of frequency of an electric field The phenol andsulfuric acid were mixed together, heated at C. for three hours, cooledto 15 C. and added to the formaldehyde which had been chilled to 0 C.,additional cooling being provided to keep the temperature below 20 C.The mixture was a reddishbrown, oily liquid. It may be stored for weeksat 5 C. The liquid was poured into a cylindrical glass mold andpolymerized at 60 C. until black in color. The resulting rod wasconditioned by soaking in distilled water and then in 2 N HCl andfinally was washed free from HCl with distilled water. The resistance ofthis water-saturated rod was measured in a direct current, and inalternating currents of varying frequencies. It was found to decrease ata rate of 4.7 10- ohm-seconds per cycle in the range of 1,000 to 20,000cycles per second, the variation being shown in thegraph of Figure '2.This method permits one to measure the frequency of an appliedalternating current (Fig. 3) by measuring the resistance of-acalibratedresin rod.

Having thus disclosed our invention and described in detail preferredembodiments thereof, we claim and desire to secure by Letters Patent:

A frequency meter comprising a solid unfractured structure comprising asan essential part extending-substantially throughout, a predominantamount of a homogeneous continuous phase of an ion exchange resin whichcomprises: an insoluble infusible synthetic organic polymeric matrix,dissociable ionic groups chemically bonded to said matrix, and water ingel relationship with said matrix; said groups having a dissociationconstant of at least 10- and being present in an amount of at leastReferences Cited in the file of this patent UNITED STATES PATENTS680,233 Doane Aug. 13, 1901 682,351 Chesney et a1 Sept. 10, 1901 770,033Wood Sept, 13, 1904 1,902,496 FitzGerald Mar. 21, 1933 2,614,976 Patnodeet al. Oct. 21, ,1952 2,636,851 Juda et a1 Apr. 28, 1953

